The present invention relates to an improved construction of oil infeed device for a hydraulic servo motor of an adjustable pitch propeller.
In the arrangement of the present invention the servo motor is drivable via a hollow intermediate shaft which is arranged within a bore in a housing member secured against rotation. Two oil supply passages in the housing member are connectable to control means for the oil supply and each open into a respective annular passage extending about the circumference of the intermediate shaft. Each annular passage is formed intermediate two axial sections of a distributor ring or ring structure supported at the intermediate shaft. The distributor ring is sealingly guided in the bore of the housing member by annular sealing ledges which extend along the exterior circumference of the distributor ring to both sides of each annular passage. The annular or ring-shaped passages each are in communication with working spaces or chambers of the servo motor through connecting passages or channels formed in the intermediate shaft.
In an oil infeed device as known, for example, from U.S. Pat. No. 2,781,857, granted Feb. 19, 1957, the annular passages extending along the intermediate shaft are arranged in a distributor ring forming a rigid sleeve and which is provided, in addition to sealing rings extending at the exterior circumference thereof, with corresponding sealing rings arranged in grooves at the interior circumferential face or surface of the distributor ring. Thus, the annular passages are sealed at the region of the running surfaces of the intermediate shaft in axial direction with respect to each other and with respect to the surroundings. In the state-of-the-art design of the oil infeed device, the inner sealing rings which are arranged intermediate the stationary sleeve and the rotating intermediate shaft are particularly subjected to considerable wear, and thus, require, due to the necessary relatively frequent exchange of the sealing rings which are accessible only with difficulty, a correspondingly great amount of assembly and maintenance work since, whenever the sealing rings have to be exchanged, the intermediate shaft has to be disassembled.
In another design of an oil infeed device as known, for example, from U.S. Pat. No. 2,786,539, granted Mar. 26, 1957, the two annular passages or channels are formed in two distributor rings separated from one another, each of which, however, is rotatably journalled with the outer circumferential surface thereof in a housing member, and each of which is sealingly and rigidly connected for rotation with the propeller shaft by two sealing rings arranged on both sides of the respective annular passage. Each of the distributor rings is arranged between two annular-shaped sealing units each comprising a sealing washer engaging the wall of the bore in the housing member and a sealing ring engaging the respective end wall of the distributor ring. Apart from the disadvantageous arrangement of the sliding surfaces or faces at the outer circumference instead of at the inner circumference of the distributor rings, the sealing rings which coact with the rotating distributor rings and which are stationarily held in the housing also, in this known design, constitute members which are subjected to wear. Consequently, they have to be exchanged rather frequently, which exchange operation requires each time disassembly of the propeller shaft. Furthermore, the oil, which is heated in the bearing gaps or clearances, cannot flow off to the exterior in this prior art design, since the pressure prevailing between the distributor ring and the sealing units in each case is the same as in the related annular passage.